This invention relates to a dual lid assembly for closing two interconnectable openings and serves in particular for coupling a container, accommodating radioactive or toxic materials, to a hot cell. The dual lid assembly is of the type which has lower and upper halves (hereafter referred to as "lower lid" or "first lid" and "upper lid" or "second lid", respectively) that may be connected to one another in a fluid-tight manner by an externally actuated mechanism. The lower lid which is oriented towards the container, can be locked to the inner side of the container wall by means of an externally actuated mechanism with the interposition of an actuating element disposed in the container and displaceable parallel to the longitudinal axis thereof.
An important problem in nuclear installations is the contamination-free removal and introduction of radioactive materials, particularly radioactive wastes, from glove boxes or hot cells into non-contaminated spaces. Because of the extremely high likelihood or contamination between the glove boxes and hot cells and the adjoining handling space, the solution of this problem involves stringent requirements regarding the fluid-tight nature of the systems. In a particular example, the significantly contaminated radioactive wastes are to be removed from the treating cell of a decontamination device into the charging and discharging cell of the waste containers. The containers for the radioactive wastes have to be contamination-free on the outside to comply with storage requirements concerning terminal dumps. In the cell itself activities having an order of magnitude of a few thousand Ci's are usually present.
A known dual lid system of the above-outlined type is actuated by compressed air for positioning a sheet metal lid on an iron-hopped barrel. The upper side of the sheet metal lid is to be maintained uncontaminated; this is achieved by means of a counter lid operated by compressed air. This system is disadvantageous in that the lid requires an O-ring seal and that the shape of the lid is cylindrical. As a result, upon positioning the lid on the barrel, the air in the barrel is compressed so that the lid, upon releasing the barrel, tends to snap out of its position and thus the sealing effect is lost. This is disadvantageous in that the llid is no longer "alpha-tight" and in case the barrel is tilted or tips over, the lid loses its force-locking relationship with the barrel.
There is known another dual lid system which makes possible the positioning of the lid in a force-locking manner but which, however, has a very complex mechanism. A proper operation of this lid system depends on very accurate tolerances of the barrel since the latter, although it is a commercially available sheet metal barrel, can be improved with regard to its tolerances only in a very expensive manner. The mechanism of this dual lid system depends on complex electric switching operations, so that even in case of minor malfunctions, major damages in the structure may result. Further, difficulties are encountered in the coupling of the two lids in case malfunctions occur or if tolerances are exceeded. This results in a substantial danger of contamination.